Under the Hood: Dealer can't pinpoint why engine stumbles

Question: In May 2017, my wife and I purchased a brand-new Newmar Baystar Sport Class A motor home. The very minute I took delivery and drove past the curb, the Ford Triton V-10 6.8-liter motor would stumble and almost die on takeoff from a stop.

Written by By Brad Bergholdt

Question: In May 2017, my wife and I purchased a brand-new Newmar Baystar Sport Class A motor home. The very minute I took delivery and drove past the curb, the Ford Triton V-10 6.8-liter motor would stumble and almost die on takeoff from a stop.

It did this on my first two takeoffs from red lights. I immediately returned to the selling dealer, but the motor home did not emulate the same problem on their test ride. I then drove it 70 miles home without incident.

Since then, the motor home has displayed the same problem intermittently numerous times. It might go 1,000 or more miles without the problem occurring, but at other times, it could occur seven times in 40 miles. I found that if I slam the vehicle's accelerator to the floor after it stumbles, it usually will take off and run in a normal fashion.

The onboard computer does not record the problem, nor has a Ford mechanic experienced the problem on a test ride. Most recently the problem has advanced to be more of a concern. On a trip from Oregon to Arizona, the motor home ran great for about 2,500 miles. Yet, twice on the latter stages of the return trip, while climbing up mountains, the motor totally shut down. Within a few seconds while still rolling forward, I jammed the accelerator twice to the floor, and the engine took off once again. This has created a very real concern for me.

If I were passing a car on a two-lane road, such hesitation could lead to a head-on collision. Or if I were on a curve or even needed to brake, I'd lose my power steering and power brakes, and that could lead to a serious accident. Ford seems unconcerned about the problem and will not do a buy-back of this dangerous vehicle.

I am hopeful that you might be able to identify the problem and possible solution for me. I really am afraid of an accident that could lead to serious injury or death for my wife and me, as well as occupants of other vehicles that could be involved in the potential accident. Thanks for any and all input.

- David F.

Answer: Wow! I can relate to your stress level. My motor home began doing similar things while driving home from Alaska. It keeps your heart racing the entire time while driving, especially during tricky single-lane, no-turn-out mountain crossings. And it was tough to fix.

A possible solution to this is a scan tool data movie, triggered at the time of symptoms. Ford dealer technicians use a VCM II, a vehicle communication module, to network a laptop or tablet to the vehicle's PCM, or powertrain control module, allowing comprehensive monitoring and control functions, The VCM also has a built-in customer flight recorder, or CFR, that requires an operator pendant. The VCM and pendant can be lent to the customer for an intermittent situation such as this.

Dealers are understandably reluctant to hand over such an expensive and useful tool, as David indicated in a follow-up communication, as was Ford customer service. Depending on the type of fault, there's a decent chance the cause, or at least some useful indicators, would show up during a follow-up data movie review.

Too bad it's not a Honda. Their cars automatically record a great data movie whenever the check engine light illuminates. With prior setup by a technician, a future movie can be triggered by a stall-out or particular parameter irregularity.

The best bet to resolve this is to keep meticulous records of each incidence, including driving conditions, run time, fuel level, accessories in use, road bumps and turns, and then turn up the heat on Ford corporate to man up and put a CFR into play for this unacceptable situation.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Email him under-the-hood@earthlink.net. He cannot make personal replies.